Field of the Invention
The use of plant protection formulations comprising biological control agents (BCAs) has become a valuable alternative in the field of plant protection. Biological control agents directed against fungi or insects as well as those promoting plant health have been put on the market in different formulations.
Description of Related Art
The provision of suitable formulations for biological control agents nevertheless still pose a challenge due to the many factors contributing to the efficacy of the final formulation such as form of the biological control agent, temperature stability and shelf life as well as effect of the formulation in the application.
Suitable formulations are homogeneous and stable mixtures of active and inert ingredients which make the final product simpler, safer, and more efficacious to apply to a target. Commonly used additives in formulations include surfactants such as dispersants or wetting agents, solvents, emulsifiers, defoamers and stabilizers
Commonly used formulations for biological control agents include WP, a solid formulation micronized to powder form and typically applied as suspended particles after dispersion in water, and WG, a formulation consisting of granules to be applied after disintegration and dispersion in water. The granules of a WG product has distinct particles within the range 0.2 to 4 mm. Water dispersible granules can be formed by agglomeration, spray drying, or extrusion techniques.
WP formulations are produced rather easily but they are dusty. Further, they are not easy to dose in the field. WG formulations are easier to handle for the user and in general have lower dust content than WP formulations.
An example for a liquid formulation is SC, a water-based suspension of solid active ingredient in a fluid usually intended for dilution with water before use. In such formulations, the active ingredient tends to settle over time and this is the reason why thickeners are used. Another liquid formulation type is EC, a solution of active ingredient combined with surfactants like e. g. emulsifying agents in a water insoluble organic solvent which will form an emulsion when added to water. Such formulation tends to be more hazardous to the operator and the environment due to the organic solvents used.
An enormous number of formulants have been utilized in experimental and commercial formulations of biological control agents (for a more detailed description and list see Schisler et al., Phytopathology, Vol 94, No. 11, 2004). Generally, formulants can be grouped as either carriers (fillers, extenders) or formulants that improve the chemical, physical, physiological or nutritional properties of the formulated biomass. A comparison of formulations and their effect on Trichoderma harzianum can be found in Küçcük and Kivaniç (African Journal of Biotechnology 2005, Vol. 4 (5), pp. 483-486).
Another example for a formulation of a biological control agent is described in Tones et al., 2003, J Appl Microbiol, 94(2), pp: 330-9). However, it is clear that a formulation preserving a viability of the biological control agent, e. g. spores, of more than 70% for 4 months at 4 degrees C. only is not suitable for everyday use in the field. Rather, it is desirable that formulations of biological control agents have a sufficient shelf life even under conditions where cold storage is not possible.